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Insulin signaling pathways in lepidopteran ecdysone secretion
Wendy A Smith1, Anthony Lamattina1, McKensie Collins1
1Department of Biology, Northeastern University Boston, MA, USA.
Frontiers in Physiology
|February 20, 2014
Summary
Insect molting involves ecdysteroid hormones, with insulin signaling playing a role. Studies in Bombyx moths show insulin and PTTH intersect, unlike in Manduca sexta, revealing species-specific hormonal regulation of insect development.
Area of Science:
- Insect physiology
- Endocrinology
- Developmental biology
Background:
- Molting and metamorphosis are regulated by ecdysteroid hormones secreted by prothoracic glands.
- Insulin-like hormones can modulate prothoracic gland activity, linking development to nutritional status.
- In silk moths (Bombyx mori), insulin and bombyxin directly stimulate prothoracic glands, and PTTH acts via the insulin-signaling pathway.
Purpose of the Study:
- To investigate the role of the insulin-signaling pathway in ecdysone secretion in Manduca sexta prothoracic glands.
- To compare the mechanisms of ecdysone regulation between Bombyx mori and Manduca sexta.
- To elucidate species-specific differences in hormonal control of insect molting.
Main Methods:
- Utilized inhibitors of phosphatidylinositol-3-kinase (PI3K), LY294002 and wortmannin, in Manduca sexta prothoracic glands.
- Assessed the effects of PI3K inhibitors on Akt and 4EBP phosphorylation and ecdysone secretion.
- Examined the impact of MEK and RSK inhibitors (U0126, SL0101) on ecdysone secretion and ERK phosphorylation.
Main Results:
- In Manduca sexta, insulin stimulates insulin receptor and Akt phosphorylation but not ecdysone secretion.
- PI3K inhibition blocked Akt and 4EBP phosphorylation without affecting ecdysone secretion in Manduca sexta.
- Inhibitors of ERK and RSK signaling pathways significantly inhibited ecdysone secretion in Manduca sexta, unlike in Bombyx mori.
Conclusions:
- The insulin-signaling pathway plays a distinct role in Manduca sexta compared to Bombyx mori regarding ecdysone secretion.
- PTTH action is separate from insulin signaling in Manduca sexta, contrasting with Bombyx mori where they intersect.
- Significant species differences exist in the regulation of insect ecdysone secretion, involving translational regulators and MAPkinase pathways, and the impact of insulin on molting control.
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